Evolutionary impact of small RNA-dependent gene expression in bryophytes during the molecular adaptation for life on land

• Applicant: Professor Dr. Wolfgang Frank
• Subject Area: Evolution and Systematics of Plants and Fungi ; Plant Physiology ; Plant Cell and Developmental Biology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 440035902

Evolutionary impact of small RNA-dependent gene expression in bryophytes during the molecular adaptation for life on land We will perform comparative analyses of small RNA-dependent regulatory pathways in two bryophyte species, the moss Physcomitrium patens and the liverwort Marchantia polymorpha. The project involves functional studies on specific DICER-LIKE dependent small RNA (sRNA) pathways and the characterisation of their targets. Analyses of a specific P. patens PpDCL1a mutant that lacks an autoregulatory feedback loop revealed an essential contribution of this control of miRNA biogenesis in the adaptation to salt. Transcriptome analyses in the mutant allowed the identification of genes that contribute to adaptive processes required for the water-to-land transition. Alterations in the expression levels of two of these genes encoding a flotillin-type membrane protein (PpFLOT) acting in vesicle transport and signalling and a MYB transcription factor (PpMYB), respectively, led to altered growth and impaired sensitivity to salt as well as to phytohormones. The underlying molecular mechanisms causing these phenotypic abnormalities will be explored. Further, we generated mutant lines for all four known M. polymorpha DCL genes and detected severe abnormalities of these mutant lines with respect to development, phytohormone response and salt sensitivity. The Mpdcl mutants present a valuable tool for the dissection of all sRNA pathways in M. polymorpha and their comparison with already analysed sRNA pathways in P. patens. We will use the Mpdcl lines for genome-wide sRNA and mRNA transcriptome profiling to elucidate the specific sRNA repertoire and sRNA-mediated gene control in the liverwort M. polymorpha. Based on our initial analyses of the sRNA-dependent genes in P. patens and the preliminary work on Mpdcl mutant lines we expect to address several key aspects of the MAdLand priority program including the evolution of phytohormone-related signalling and associated control of gene expression, the increase in body plan complexity as well as the evolution of regulatory mechanisms related to the adaptation to new environments.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2237: MAdLand — Molecular Adaptation to Land: plant evolution to change